The techniques related to the first to tenth embodiments of the present disclosure are disclosed in the following Patent Documents 1 to 4.
<Patent Document 1>
Patent Document 1 discloses a dual rotor type motor. Patent Document 1 discloses a technique of independently driving an inner rotor and an outer rotor by a composite current that combines currents corresponding to the respective rotors. However, the motor of Patent Document 1 is for an automobile, and a stator of the motor is constituted by the number of independent cores that are larger than the number of poles of the inner rotor and the outer rotor.
<Patent Document 2>
Patent Document 2 discloses a motor for rotating and driving a drum and a pulsator of a washing machine in a direct-drive type (a type in which the drum and the pulsator are directly driven by a motor without passing through a complicated transmission mechanism).
The motor of this washing machine has a structure in which an outer rotor type washing motor (to drive the pulsator) and an inner rotor type dewatering motor (to drive the drum) are disposed inside and outside. Two stators for the washing motor and the dewatering motor are provided in a stator unit disposed between the rotors of the two motors.
During the washing operation in which the washing process and the rinsing process are performed, a large amount of water is filled in the drum, so that the motor is required to have a high torque at a low speed. On the other hand, during the dewatering operation, since the water in the drum is removed, the motor can be driven at a low torque, but a high-speed rotation is required for the motor. Therefore, the washing machine motor is required to have a specific output performance corresponding to the low speed-high torque and the high speed-low torque.
Accordingly, in this washing machine, the dewatering motor which does not require a high torque is arranged in the form of an inner motor, and the washing motor is arranged in an outer rotor shape in which the outer diameter of the rotor is large and high torque is obtained, thereby realizing the appropriate output performance.
During the washing process and the rinsing process requiring high torque, the washing machine controls the pulsator to rotate while reversing forward and reverse in a state in which the drum is kept from rotating in the same manner as in the conventional control.
During the dewatering process, rotations of the washing motor and the dewatering motor are shifted from each other. When the rotational speeds of the two motors are different from each other by a predetermined speed or more, the motor having the smaller rotational speed is controlled to become similar to the rotational speed of the other motor.
In the dewatering process, the washing motor and the dewatering motor are synchronously operated, and at the timing when the washing motor reaches the predetermined rotational speed, only the dewatering motor is driven and the supply of current to the washing motor is stopped so that the washing motor is in the rotation-free state.
<Patent Document 3>
Patent Document 3 discloses a method of manufacturing a stator of a dual rotor type motor.
Specifically, eighteen stator cores wound with coils are formed by winding a coil on a prismatic stator core having insulator members (insulating materials) mounted on both ends thereof. In the state where the eighteen stator cores wound with the coils are arranged in the circumferential direction, the both ends of the stator cores are sandwiched between a pair of annularly shaped gallery plates and the gallery plates are fixed with bolts or nuts while performing insulation measures, thereby forming a stator skeleton structure.
In order to fix the stator core to an appropriate position, convex portions extending in the axial direction are formed on the inner and outer surfaces of the stator core. When these convex portions are fitted in the concave portions provided in the stator molding container, the stator skeleton structure is inserted into the stator molding container. Thereafter, when the space between the stator molding container and the stator skeleton structure is filled with resin, a resin molded product is formed.
Since the convex portions remain in the resin molded product, when the convex portions are mechanically removed, the stator is completed.
<Patent Document 4>
Patent Document 4 discloses a vertical type washing machine in which a drum is rotated during a washing process or a rinsing process. In this washing machine, since both the drum and the pulsator are driven by a single motor, during the washing process or the rinsing process, in contrast to the conventional control, only the drum is rotated while reversing the forward and backward directions in a state in which the pulsator is fixed and is not rotated. Further, during dewatering process, the pulsator is released from the fixation, the drum is rotated at a high speed in a state in which the pulsator is rotatable.